Optical systems and devices generally comprise optical assemblies (OAs) of opto-electric devices (OEDs) integrated with optical conduits, such as fibers and waveguides, on a substrate or platform. Critical to the effectiveness of these OAs is the alignment of the OED with this optical conduit. There are generally two alignment approaches for aligning OEDs—active and passive. In passive alignment, registration or alignment features are typically fabricated directly on the components as well as on the platform to which the components are to be mounted. The components are then positioned on the platform using the alignment features and affixed in place. In active alignment, the OEDs are placed on the platform, but before being affixed thereto, an optical signal is transmitted through the components while they are manipulated to provide optimum optical performance. Once optimum performance is achieved, the components are affixed to the platform. Although active alignment tends to be more precise than passive alignment, passive alignment facilitates high-speed, high-volume automated manufacturing and, thus, is preferred.
One of the preferred set of OEDs in the optical communication technology is the surface emitting and detecting device. However, devices such as Vertical Cavity Surface Emitting Lasers (VCSELS) and photo detectors (such as PIN photodiodes) that have the photosensitive surface to receive or emit light on the top surface tend to be difficult to align with an optical fiber. In general, to effect the alignment between the device and the fiber using a silicon optical bench, the device must be on a different plane than the fiber, with the light being communicated therebetween by a reflective surface. While such technology has its merits in allowing passive alignment to some extent, it typically requires that the device be actively aligned into position so that light is properly reflected by the reflective surface. Furthermore, the use of a reflective surface decreases coupling efficiency due to intrinsic losses incurred at each optical surface through dispersive effects.
Accordingly, there is a need for a more efficient system to optically couple fiber and the device. One such system is disclosed in U.S. Pat. No. 5,905,831, which is hereby incorporated by reference. The '831 patent discloses a system in which the surface emitting OED is mounted on a passive alignment member, which in turn is mounted to a substrate containing a fiber, thereby passively aligning the OED with a fiber held in the substrate.
Although such a system provides for passive alignment and manufacturability, Applicants have identified the need to further simplify the system, improve optical performance (reduce insertion loss) and to further enhance manufacturability. The present invention fulfils these needs among others.